Process for the sequential hydroconversion and hydrodesulfurization of whole crude oil

ABSTRACT

The invention relates to a method for removing sulfur from crude oils using a catalytic hydrotreating process operating at moderate temperature and pressure and reduced hydrogen consumption. The process produces sweet crude oil having a sulfur content of between about 0.1 and 1.0 wt % in addition to reduced crude density. The method employs least two reactors in series, wherein the first reactor includes a hydroconversion catalyst and the second reactor includes a desulfurization catalyst.

RELATED APPLICATIONS

This application is a continuation-in-part of U.S. Non-provisionalpatent application Ser. No. 12/501,300, filed Jul. 10, 2009, attorneydocket number 004159.003095, which claims priority to U.S. ProvisionalPatent Application Ser. No. 61/080,582, filed Jul. 14, 2008, all ofwhich are incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to a process for the hydrodesulfurizationof sour crude oils using a catalytic hydrotreating and desulfurizationprocesses operating at moderate temperature and pressure and at reducedhydrogen consumption.

BACKGROUND OF THE INVENTION

The removal of sulfur compounds from crude oil and its fractions hasbeen of significant importance for several decades, but has become evenmore important in recent years due to tightening environmentallegislation. While much of the prior art focuses on the desulfurizationof individual crude oil fractions, a large segment of the art hasaddressed processes for the hydroprocessing of whole crude oil. Themajority of the interest in recent years has focused on the upgrading ofvery heavy crude oil (i.e., API gravity<20), shale and tar-sands, toproduce light sweet synthetic crudes. One major driving force for theseprocesses is the demand for light crude oils in refineries and the lowvalue of highly viscous feedstocks. Furthermore, refinery demands areshifting from high sulfur fuel oils to low- and ultra-low sulfurproducts, i.e., products containing about 1 wt % (LSFO) and about 0.5 wt% (ULSFO). Therefore, the ability to produce LSFO or ULSFO, instead ofhigh sulfur fuel oils, is highly advantageous and desired.

One major technical challenge posed when hydrotreating heavy oilfractions or whole crude is the effect of small concentrations ofcontaminants, such as for example, organic nickel and vanadiumcompounds. These organometallic compounds and others have been proven toreduce the activity or lifetime of hydrotreating catalysts.

Another major challenge faced during the processing of whole crude oilis that the concentration of coke precursors can generally be very high.These coke precursors, such as for example, asphaltenic plates, canreduce the activity or lifetime of hydro-desulfurization (HDS)catalysts. This results in a decreased performance of a conventionalprocess over time, thus requiring more frequent addition or replacementof catalyst to ensure continued operation. Catalyst replacement can beboth costly and time consuming, thereby reducing the overall economicfeasibility of the process.

Generally, deactivation of catalyst within a hydroprocessing unittypically occurs by one of two primary mechanisms: (1) metal depositionand (2) coke formation. For each mechanism, increasing the operatingtemperature of the hydroprocessing unit can help maintain catalystperformance; however, all process units have maximum temperature limitsbased upon the metallurgy of the process unit. These maximumtemperatures limit the amount of time a catalyst can operate beforerequiring catalyst replacement, typically by either the regeneration ofspent catalyst or the addition of fresh catalyst. Furthermore, thereplacement of spent catalyst with fresh catalyst can require thecomplete shutdown of a process unit in order to unload the deactivatedspent catalyst and load fresh catalyst into the unit. This process unitdowntime reduces the on-stream time and negatively impacts the economicsof the process.

SUMMARY

Provided is a process for the desulfurization of sour crude oils using acatalytic hydrotreating process. The method includes the steps of (a)contacting a crude oil feedstock with hydrogen gas to produce a hydrogengas crude oil mixture; (b) contacting the hydrogen gas crude oil mixturewith a hydroconversion catalyst in a first reactor maintained at atemperature of between about 400° C. and 450° C. to produce an effluenthaving an asphaltene content of less than 5% by weight, wherein saidhydroconversion catalyst includes a bimodal support material; (c)contacting the effluent from the first reactor with hydrogen gas toproduce a effluent hydrogen gas mixture; (d) contacting the effluenthydrogen gas mixture with a desulfurization catalyst in a second reactorto produce an upgraded crude oil product having a reduced sulfur contentand an increased API gravity, wherein said second reactor is maintainedat a temperature that is less than the temperature that is maintained inthe first reactor.

The hydroconversion catalyst can further include a base metal selectedfrom the group consisting of a group VB metal, a group VIB metal and agroup VIIIB metal and wherein the bimodal support material includes afirst pore size having an average diameter of between about 6000 and10000 Angstroms and a second pore size having an average diameter ofbetween about 80 and 150 Angstroms. The hydroconversion catalyst canalso include a promoter metal, wherein the promoter metal is selectedfrom the group consisting of a group IIB metal, a group IVB metal and agroup VIIIB metal, and wherein the promoter metal is present in anamount between about 1 and 3% by weight. The hydroconversion catalystcan include a molybdenum base metal in an amount of between about 7.5and 9% by weight, and a nickel promoter metal in an amount of betweenabout 1 and 3% by weight.

The hydrodesulfurization catalyst can include a base metal selected froma group VB, VIB or VIIIB metal. The hydrodesulfurization catalyst canalso include a support material having an average pore size of betweenabout 100 and 300 Angstroms. The hydrodesulfurization catalyst can alsoinclude a promoter metal, wherein said promoter metal is selected fromthe group consisting of a group IIB metal, a group IVB metal and a groupVIIIB metal, and wherein the promoter metal is present in an amountbetween about 1 and 3% by weight. The hydrodesulfurization catalyst caninclude a molybdenum base metal in an amount of between about 9 and 11%by weight, and a nickel promoter metal in an amount of between about 2and 3% by weight.

In another aspect, a method for upgrading crude oil is provided. Themethod includes the steps of (a) contacting a crude oil feedstock withhydrogen gas to produce a hydrogen gas crude oil mixture; (b) contactingthe hydrogen gas crude oil mixture with a hydroconversion catalyst in afirst reactor, wherein the hydroconversion catalyst includes a supportmaterial having a bimodal pore size wherein the first pore size isbetween about 6000 and 10000 Angstroms and the second pore size isbetween about 80 and 150 Angstroms, and wherein the first reactor ismaintained at a temperature of between about 400° C. and 450° C. toproduce an effluent having an reduced asphaltene concentration relativeto the crude oil feedstock; (c) contacting the effluent from the firstreactor with hydrogen gas to produce an effluent hydrogen gas mixture;and (d) contacting the effluent hydrogen gas mixture with adesulfurization catalyst in a second reactor to produce an upgradedcrude oil product having a reduced sulfur content and an increased APIgravity, wherein the second reactor is maintained at a temperature thatis less than the temperature that is maintained in the first reactor.

The hydroconversion catalyst can include a base metal selected from agroup VIIIB metal and a bimodal support material, wherein the bimodalsupport material includes a first pore size having an average diametergreater than at least about 2000 Angstroms and less than about 15000Angstroms and a second pore size having an average diameter of betweenabout 50 and 250 Angstroms. The hydrodesulfurization catalyst caninclude a base metal selected from the group consisting of a group VBmetal, a group VIB metal and a group VIIIB metal and a catalyst supportmaterial having an average pore size of between about 100 and 300Angstroms.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram of one embodiment of a system for upgrading a wholecrude oil.

FIG. 2 is a diagram of another embodiment of a system for upgrading awhole crude oil.

FIG. 3 shows the net conversion of the fraction of hydrocarbons having aboiling point greater than 540° C. according to one embodiment of theprocess.

FIG. 4 shows expected hydrodesulfurization according on one embodimentof the process.

DETAILED DESCRIPTION OF THE INVENTION

Although the following detailed description contains many specificdetails for purposes of illustration, one of ordinary skill in the artwill appreciate that many variations and alterations to the followingdetails are within the spirit and scope of the invention. Accordingly,the exemplary embodiments of the invention described herein are setforth without any loss of generality to, and without imposinglimitations thereon, the claimed invention.

Described is a process is provided for the upgrading of whole crude oil,which can include the use of a series of at least two reactors, forexample, ebullating bed reactors. The reactors employ differentcatalysts, and thus target different kinetic regimes, such as forexample, the hydroconversion and hydrodesulfurization of whole crude oilfeedstock.

The first reactor can include a hydroconversion catalyst that isselective for the conversion of high boiling hydrocarbons, particularlyfor the hydroconversion of hydrocarbon fractions having a boiling pointgreater than about 540° C. Typically, the catalyst employed in the firstreactor is selective for the conversion of hydrocarbon fractions havinga boiling point greater than about 540° C., and converts heavy materialpredominantly via thermal cracking. In certain embodiments, thehydroconversion catalyst employed in the first reactor can be operatedsuch that the asphaltene content of the effluent from the first reactoris reduced to less than 10% by weight of the effluent, preferably lessthan 8% by weight, and even more preferably less than about 5% byweight. In certain embodiments, the asphaltene content of the effluentfrom the first reactor is reduced to less than 4% by weight of theeffluent, preferably less than 3% by weight. Use of hydroconversioncatalysts in the first reactor, as noted above, is also advantageousbecause the catalyst used also acts as a pretreatment for the secondstage.

Generally, the second reactor includes a catalyst that is selective forhydrodesulfurization of the whole crude feed. The reactor conditions andthe catalyst selected are operable to specifically remove sulfur fromthe liquid product, thereby producing an upgraded whole crude oil, orsynthetic crude oil, having both a reduced sulfur content and anincreased API gravity, as compared with the feedstock.

FIG. 1 shows an exemplary method of operation where a whole crude oilfeedstock is upgraded. Whole crude oil feed 14 is contacted withhydrogen gas 12 at a pressure of between about 50 and 150 bar to createa crude oil/hydrogen gas mixture 16. In certain embodiments, thehydrogen gas pressure is less than about 120 bar. Alternatively, thehydrogen gas pressure is maintained between about 75 and about 125 bar,or between about 85 and 110 bar. In yet other embodiments, the hydrogengas pressure is maintained at about 100 bar. Crude oil/hydrogen gasmixture 16 is supplied to first reactor 18, preferably being suppliedupwardly to a first ebullating bed reactor that includes ahydroconversion catalyst, although it is understood that other reactordesigns can also be employed. In certain embodiments, thehydroconversion catalyst employed in first reactor 18 is selective forthe conversion of hydrocarbons having a boiling point greater than 540°C.

Fresh and/or regenerated hydroconversion catalyst can be added to firstreactor 18 via line 20. Spent catalyst can be withdrawn from the bottomof first reactor 18 via line 24, or by other known means. In certainembodiments, spent catalyst withdrawn via line 24 can optionally beregenerated offline. Optionally, the catalyst regenerated offline can beresupplied back to first reactor 18. In other embodiments, freshcatalyst and regenerated catalyst can be supplied to the first reactor18 via make-up line 24 to replace spent and/or withdrawn catalyst.

First reactor 18 can be operated at a temperature of between about 350°C. and 450° C., and in certain embodiments can achieve conversion of upto about 50% of the hydrocarbon material having a boiling point aboveabout 540° C. in the crude oil feedstock. In other embodiments, thetemperature can be maintained between about 375° C. and 425° C. In yetother embodiments, the temperature can be maintained at about 400° C.Alternatively, the temperature can be maintained between about 400° C.and 425° C. In certain embodiments, the first reactor is operated at atemperature greater than about 400° C. In certain embodiments, theeffluent from the first reactor 18 has an asphaltene content of lessthan about 5 wt %.

Effluent 22 from first reactor 18 is contacted with hydrogen gas 26, andthe resulting effluent-hydrogen gas mixture is fed to second reactor 28,preferably being fed upwardly to an ebullating bed reactor that includesa hydrodesulfurization catalyst, although it is understood thatalternate reactor designs can also be employed. Fresh and/or regeneratedhydrodesulfurization catalyst can be added to second reactor 28 via line30, and spent catalyst can be withdrawn from the second reactor via line34. Spent catalyst withdrawn from second reactor 28 can optionally beregenerated offline and resupplied to the second reactor. In oneembodiment, second reactor 28 can be operated at a temperature ofbetween about 350° C. and 450° C. In other embodiments, second reactor28 is operated at a temperature below about 400° C., and in certainother embodiments, the second reactor is operated at a temperaturesbelow about 390° C. Optionally, second reactor 28 is operated at atemperature between about 375° and 400° C. Second reactor 28 can beoperated at a pressure of between about 50 and 150 bar. In certainembodiments, second reactor 28 is operated at a pressure of betweenabout 80 and 120 bar. In yet other embodiments, second reactor 28 isoperated at a pressure of about 100 bar. The final liquid product fromsecond reactor 28 can be collected via line 32 as an upgraded crude oilproduct having a sulfur content of about 0.1 to 1 wt % and an API thathas been increased by at least about 2 degrees, relative to the crudeoil feedstock. It is understood that the first and second reactors canbe any known vessels suitable for hydroconversion orhydrodesulfurization of a crude oil feedstock. In certain embodiments,at least one of the reactors is an ebullating bed reactor.

In certain embodiments, the temperature of the first reactor is higherthan the temperature of the second reactor. For example, the firstreactor can be maintained at a temperature of between about 400° and425° C. and a pressure of between about 80 and 120 bar, and the secondreactor can be maintained at a temperature of less than about 400° C.,and a pressure of about between about 80 and 120 bar. In anotherembodiment, wherein the pressure of the first and second reactors ismaintained at between about 80 and 120 bar, the temperature of the firstreactor is maintained at between about 405° and 420° C. and thetemperature of the second reactor is maintained between about 380° and400° C. In yet another embodiment, wherein the pressure of the first andsecond reactors is maintained at about 100 bar, the temperature of thefirst reactor is maintained at between about 410° and 420° C. and thetemperature of the second reactor is maintained at between about 380°and 390° C. In certain embodiments, maintaining the temperature of thesecond reactor at less than about 400° C. may improve the equilibrium ofthe reaction.

In certain embodiments, first reactor 18 and second reactor 28 can beoperated at substantially similar reaction conditions with respect tooperating temperatures and pressures. Alternatively, first reactor 18and second reactor 28 can be operated at substantially differentreaction conditions with respect to operating temperatures andpressures.

Referring to FIG. 2, whole crude fraction 12 is combined with hydrogengas 14 and supplied via line 16 to first reactor 18. The first reactor18 can be an ebullating bed reactor charged with a hydroconversioncatalyst, as previously described with respect to FIG. 1. Catalyst isadded to first reactor 18 via line 20 and removed from the reactor vialine 24. The effluent 22 from first reactor 18 can be supplied tointer-stage separator 40, which is operable to remove light gases, suchas for example, H₂S, NH₃ and hydrocarbons having fewer than five totalcarbon atoms, via line 41. Heavier compounds that are not removed by theinter-stage separator 40 can be mixed with hydrogen gas 26 and suppliedvia line 27 to second reactor 28. As described with respect to FIG. 1,second reactor 28 can include a desulfurization catalyst. Fresh orregenerated catalyst can be added to second reactor 28 via line 30, andspent catalyst can be withdrawn via line 34. The resulting desulfurizedcrude can be collected from second reactor 28 via line 32. Reactionconditions for the first and second reactors shown in FIG. 2 can be thesame conditions as described with respect to FIG. 1.

In certain embodiments, the effluent hydrogen gas mixture 42 from firstreactor 18 can be quenched by a liquid stream. In certain embodiments,the replacement rate of the hydrodesulfurization catalyst and thehydroconversion catalyst may be different. In certain other embodiments,the replacement rate of the hydrodesulfurization and hydroconversioncatalysts can be the same.

In certain embodiments, the catalyst can include at least two metals,wherein a first metal is a base metal and a second metal is a promotermetal. The base metal for the hydroconversion catalyst can be selectedfrom a group VB, VIB or VIIIB metal, preferably selected from chromium,molybdenum, tungsten, iron, cobalt and nickel, and combinations thereof,more preferably selected from molybdenum and tungsten. In certainembodiments, the base metal can be present in an amount between about 5and 15% by weight, preferably between about 7 and 12% by weight, morepreferably between about 7.5 and 9% by weight.

In certain embodiments, the hydroconversion catalyst can include a metalsulfide, wherein the metal is selected from the group VB, VIB or VIIIBmetals of the periodic table.

The promoter metal for the hydroconversion catalyst can be selected froma group IIB metal, a group IVA metal, or a group VIIIB metal. Exemplarygroup IIB metals include zinc, cadmium and mercury. Exemplary group IVAmetals include germanium, tin and lead. Exemplary group VIIIB metalsinclude iron, ruthenium, cobalt, nickel, palladium and platinum.Preferably, the promoter metal is selected from the group consisting ofiron, cobalt, and nickel. In certain embodiments, the promoter metal isnickel and is present in an amount between about 0.5 and 5% by weight,more preferably between about 1 and 3% by weight, even more preferablybetween about 1.5 and 2.5% by weight.

In one preferred embodiment, the base metal is selected from molybdenum,tungsten and combinations thereof, and is present in an amount betweenabout 7.5 and 9% by weight, and the promoter metal is nickel, and ispresent in an amount of between about 1 and 3% by weight.

The support material for the hydroconversion catalyst is typically moreacidic than the support for the hydrodesulfurization catalyst.Generally, the support material for the catalysts for both thehydroconversion and hydrodesulfurization can be prepared by eitherprecipitation or mulling. Precipitation and mulling are known processesfor the formation of support materials. Exemplary support materials forthe hydroconversion and hydrodesulfurization catalysts can includezeolites, amorphous silica-alumina and alumina, which can be mulled orkneaded to form a paste, which can be subsequently formed and dried forthe formation of the support material. The mulled or kneaded productscan further undergo thermal treatment, resulting in more intimatecontact between the components. In the present invention, the supportmaterial hydroconversion catalyst typically has a greater concentrationof co-mulled amorphous silica-alumina and zeolite, and is typically moreacidic, as compared with the support material for thehydrodesulfurization catalyst.

The catalyst support material can also include additional components,including binders (e.g., silica or alumina sol suspension), dielubricants (e.g., graphite or stearic acid), and pore forming additives(e.g., wood flower, starch, organic polymers, or carbon fibers).

Pore size distribution of the support material can be affected by thedrying, forming and calcining of the precipitate or formed mulled paste.The final shape and size of the pores of the support material istypically determined during the forming step and can include, forexample, extrudates, spheres (beads) or pellets. Size and shape aretypically determined and selected based upon the need for high activity,acceptable mechanical strength, and the type of reactor being employed.

The support material for the hydroconversion catalyst preferably has abimodal structure having a first pore size of greater than about 2000Angstroms, and less than about 15,000 Angstroms, preferably betweenabout 6000 and 10,000 Angstroms and a second pore size of between 50 and250 Angstroms, preferably about 80 and 150 Angstroms. The firstmesoporous pores allow larger asphaltene molecules to enter into thepore and be converted by cracking. The smaller microporous pores aresuitable for the conversion of smaller molecules (i.e., moleculessmaller than asphaltenes), and in certain embodiments, may also resultin some hydrotreatment of the hydrocarbon molecules.

In yet other embodiments, the hydroconversion catalyst can include morethan one metal or metal sulfide. Optionally, the hydroconversioncatalyst metal is present in an amount of between about 0 and 25% byweight. In other embodiments, the hydroconversion catalyst metal ispresent in an amount between about 1 and 20% by weight. Thehydroconversion catalyst can be supported on any known support material,including but not limited to, γ-alumina and/or γ-alumina and silica inthe faun of extrudates, spheres, cylinders or pellets, or the like.

In certain embodiments, only one catalyst selected from thehydrodesulfurization catalyst and the hydroconversion catalyst includesa group VIIIB metal. In other embodiments, the hydrodesulfurization andhydroconversion catalysts have a nearly identical metal content. In yetother embodiments, the amount of base metal in the hydroconversioncatalyst is greater than the amount of base metal in thehydrodesulfurization catalyst.

In certain embodiments, the hydrodesulfurization catalyst used in secondreactor 28 can be selected to preferably remove sulfur throughhydrodesulfurization reactions, while at the same time, minimizingthermal cracking.

The hydrodesulfurization catalyst can include a base metal selected froma group VB, VIB or VIIIB metal, preferably selected from chromium,molybdenum, tungsten, iron, cobalt and nickel, and most preferablymolybdenum. Optionally, the hydrodesulfurization catalyst can includemore than one metal. In certain embodiments, the catalyst can include atleast two metals, wherein a first metal is a base metal and a secondmetal is a promoter metal. In certain embodiments, the base metalpresent in the hydrodesulfurization catalyst can be present in an amountof between about 0 and 25% by weight. In other embodiments, the metalcan be present in an amount between about 1 and 20% by weight. Incertain embodiments, the base metal is present in an amount betweenabout 5 and 15% by weight, preferably between about 8 and 12% by weight,and even more preferably in an amount of between about 9 and 11% byweight. The desulfurization catalyst can include a metal sulfideselected from the group VB, VIB and VIIIB metals of the periodic table,which can be supported on any known support material, such as forexample, but not limited to, γ-alumina and/or γ-alumina and silica inthe form of extrudates, spheres, cylinders or pellets.

In certain embodiments, the hydrodesulfurization catalyst can include apromoter metal. The promoter metal can be selected from a group IIBmetal, a group IVA metal, or a group VIIIB metal. Exemplary group IIBmetals include zinc, cadmium and mercury. Exemplary group IVA metalsinclude germanium, tin and lead. Exemplary group VIIIB metals includeiron, ruthenium, cobalt, nickel, palladium and platinum. Preferably, thepromoter metal is selected from the group consisting of iron, cobalt,and nickel. In certain embodiments the promoter metal can be present inan amount between about 0.5 and 5% by weight, more preferably betweenabout 1 and 3% by weight, even more preferably between about 2.5 and 3%by weight.

The support for the hydrodesulfurization catalyst has a pore size havinga distribution range of between about 75 and 500 Angstroms, preferablybetween about 100 and 300 Angstroms. Preferably, the catalyst supporthas a monomodal pore size, resulting in a relatively uniform pore sizedistribution. The pore size of the desulfurization catalyst allows forsulfur containing molecules to enter the pores and be desulfurized,enabling for a maximization of the surface area available fordesulfurization, thereby allowing for a maximum number of active sitesto contact the sulfur containing molecules.

Generally, relative to the hydroconversion catalyst, the desulfurizationcatalyst support material has a lower acidity, having co-mulledamorphous silica-alumina and zeolite being present in larger amountsthan is found in the support material for the hydroconversion catalyst.

In an alternate embodiment, the whole crude oil feedstock can be firstsupplied to a reactor that includes a hydrodesulfurization catalystaccording to the present invention, and then supplied to a reactor thatincludes an appropriate hydroconversion catalyst according to thepresent invention.

In another embodiment, prior to supplying the crude oil to thehydroconversion reactor, the whole crude oil can be separated into twoinitial fractions, a first whole crude oil fraction having a maximumboiling point of not greater than about 250° C., and a second wholecrude oil fraction containing the balance of the whole crude oil (i.e.,material having a boiling point greater than about 250° C.). The firstwhole crude oil fraction can be removed from the whole crude oilprocesses such that the first whole crude oil fraction is supplied to aseparate reaction zone for the removal of sulfur, and can then berecombined with the second reactor effluent 32 to form a final totalliquid product having a total reduced sulfur content of preferablybetween about 0.1 and 1 wt %.

In yet another embodiment, the first whole crude oil fraction canoptionally be recombined with the effluent from the first reactor 22,contacted with hydrogen gas 26, and their supplied to the second reactor28 as a mixture consisting of whole crude oil having a boiling point ofless than about 250° C. and hydrogen gas.

EXAMPLE

An Arab heavy crude feedstock having properties as shown in Table Ibelow was processed in accordance with an embodiment of the presentinvention.

TABLE 1 Properties of Heavy Oil Feedstock Crude Origin Units ArabianHeavy Export Refractive index 1.5041 Density at 15° C. g/ml 0.8904 APIGravity ° 27 CCR wt % 8.2 Vanadium wt ppm 56.4 Nickel wt ppm 16.4 Sulfurwt % 2.8297 NaCl content wt ppm <5 C wt % 84.9 H wt % 11.89 O wt % 0.43N wt % 0.22 S wt % 2.71

The system was maintained at a total hydrogen pressure of about 100 barand the hydrogen gas to hydrocarbon feedstock ratio was maintained at aration of about 800 liters of hydrogen per liter of Arab heavy crudefeedstock. The catalyst system was maintained at a temperature ofbetween about 400° C. and 420° C. The heavy crude oil was supplied withhydrogen gas to a first reactor charged with a hydroconversion catalyst,and the effluent from the first reactor was then supplied, along withhydrogen gas, to a second reactor charged with a hydrodesulfurizationcatalyst. The liquid hourly space velocity (LHSV) for the first andsecond reactors were approximately 0.5 hr⁻¹. Net conversion of thefraction having a boiling point greater than 540° C. is shown in FIG. 3,wherein a net conversion of the crude having a boiling point of greaterthan 540° C. of approximately 45 wt % is achieved. The predictedperformance of the hydrodesulfurization reaction in the second reactoris provided in FIG. 4, which predicts that approximately 86 wt %hydrodesulfurization is achieved.

Although the present invention has been described in detail, it shouldbe understood that various changes, substitutions, and alterations canbe made hereupon without departing from the principle and scope of theinvention. Accordingly, the scope of the present invention should bedetermined by the following claims and their appropriate legalequivalents.

That which is claimed is:
 1. A method for upgrading crude oil, themethod comprising: (a) contacting a crude oil feedstock with hydrogengas to produce a hydrogen gas crude oil mixture; (b) contacting thehydrogen gas crude oil mixture with a hydroconversion catalyst in afirst reactor maintained at a temperature of between about 400° C. and450° C. to produce an effluent having an asphaltene content of less than5% by weight, wherein said hydroconversion catalyst comprises a bimodalsupport material; (c) contacting the effluent from the first reactorwith hydrogen gas to produce a effluent hydrogen gas mixture; (d)contacting the effluent hydrogen gas mixture with a desulfurizationcatalyst in a second reactor to produce an upgraded crude oil producthaving a reduced sulfur content and an increased API gravity, whereinsaid second reactor is maintained at a temperature that is less than thetemperature that is maintained in the first reactor.
 2. The method ofclaim 1 wherein the hydroconversion catalyst further comprises a basemetal selected from the group consisting of a group VB metal, a groupVIB metal and a group VIIIB metal and wherein said bimodal supportmaterial comprises a first pore size having an average diameter ofbetween about 6000 and 10000 Angstroms and a second pore size having anaverage diameter of between about 80 and 150 Angstroms.
 3. The method ofclaim 2 wherein the hydroconversion catalyst further comprises apromoter metal, wherein said promoter metal is selected from the groupconsisting of a group IIB metal, a group IVB metal and a group VIIIBmetal, and wherein said promoter metal is present in an amount betweenabout 1 and 3% by weight.
 4. The method of claim 1 wherein thehydrodesulfurization catalyst comprises a base metal selected from agroup VB, VIB or VIIIB metal.
 5. The method of claim 1 wherein thehydrodesulfurization catalyst comprises a support material having anaverage pore size of between about 100 and 300 Angstroms.
 6. The methodof claim 4 wherein the hydrodesulfurization catalyst further comprises apromoter metal, wherein said promoter metal is selected from the groupconsisting of a group IIB metal, a group IVB metal and a group VIIIBmetal, and wherein said promoter metal is present in an amount betweenabout 1 and 3% by weight.
 7. The method of claim 1 wherein the supportmaterial for the hydroconversion catalyst is more acidic than thesupport material for the hydrodesulfurization catalyst.
 8. The method ofclaim 1 further comprising the steps of supplying the effluent from thefirst reactor to an interstage separator to remove a light fractioncomprising hydrocarbons having fewer than 5 carbons, hydrogen sulfideand ammonia.
 9. The method of claim 1 wherein the API of the upgradedcrude oil product has been increased by about 2 degrees relative to theAPI of the crude oil feedstock.
 10. The method of claim 1 wherein thesulfur content of the upgraded crude oil product is reduced to betweenabout 0.1 and 1.0 wt %.
 11. The method of claim 1 wherein at least oneof the first and second reactors is an ebullating bed reactor.
 12. Themethod of claim 1 further comprising: separating the crude oil feedstockinto a first fraction and a second fraction before the crude oilfeedstock being supplied to the first reactor, wherein the firstfraction has a maximum boiling point less than 250° C. and the secondfraction has a boiling point greater than 250° C.; removing the firstfraction and processing the first section in a separate reaction zone toremove sulfur; and recombining the desulfurized first fraction with theeffluent from the second reactor.
 13. The method of claim 2 wherein thebase metal of the hydroconversion catalyst comprises molybdenum in anamount of between about 7.5 and 9% by weight, and wherein thehydroconversion catalyst further comprising a nickel promoter metal inan amount of between about 1 and 3% by weight.
 14. The method of claim 1wherein the desulfurization catalyst comprises a sulfide of a metalselected from groups VB, VIB and VIIIB of the periodic table.
 15. Themethod of claim 1 wherein at least one of the hydroconversion anddesulfurization catalyst is regenerated offline.
 16. A method forupgrading crude oil, the method comprising: (a) contacting a crude oilfeedstock with hydrogen gas to produce a hydrogen gas crude oil mixture;(b) contacting the hydrogen gas crude oil mixture with a hydroconversioncatalyst in a first reactor, wherein said hydroconversion catalystcomprises a support material having a bimodal pore size wherein thefirst pore size is between about 6000 and 10000 Angstroms and the secondpore size is between about 80 and 150 Angstroms, and wherein the firstreactor is maintained at a temperature of between about 400° C. and 450°C. to produce an effluent having an reduced asphaltene concentrationrelative to the crude oil feedstock; (c) contacting the effluent fromthe first reactor with hydrogen gas to produce an effluent hydrogen gasmixture; (d) contacting the effluent hydrogen gas mixture with adesulfurization catalyst in a second reactor to produce an upgradedcrude oil product having a reduced sulfur content and an increased APIgravity, wherein said second reactor is maintained at a temperature thatis less than the temperature that is maintained in the first reactor.17. The method of claim 15 wherein the hydroconversion catalystcomprises a base metal selected from a group VIIIB metal and a bimodalsupport material, wherein said bimodal support material comprises afirst pore size having an average diameter greater than at least about2000 Angstroms and less than about 15000 Angstroms and a second poresize having an average diameter of between about 50 and 250 Angstroms.18. The method of claim 15 wherein the hydrodesulfurization catalystcomprises a base metal selected from the group consisting of a group VBmetal, a group VIB metal and a group VIIIB metal and a catalyst supportmaterial having an average pore size of between about 100 and 300Angstroms.
 19. The method of claim 15 further comprising operating thefirst reactor at a temperature of greater than 400° C., operating thesecond reactor at a temperature of less than 400° C., and wherein thefirst and second reactors are operated at a pressure of between about 75and 125 bar.